Strategies for the management of malaria vectors by means of genetic manipulation of natural populations are under development. Although it is presently not clear precisely which strategies will emerge as the most useful, it is clear that they must be based on a sound knowledge of the genetic structure of natural vector populations. The critical issues deal with patterns of gene flow both among and within vector populations. Anopheles gambiae has been subdivided into different chromosomal forms, which may represent incipient species characterized by being to some extent reproductively isolated. It is the goal of this proposal to study patterns of gene flow in natural An. gambiae populations using microsatellite DNA, rather than chromosomal markers. Gene and genotypic frequencies for 20 microsatellite loci will be determined for 29 populations of An. gambiae occurring on a transect covering 550 km in the Republic of Mali in West Africa. These data will be evaluated relative to data on chromosome inversions and be used to formulate indirect estimates of gene flow between populations and among chromosomal forms within populations. The loci utilized have been physically mapped to polytene chromosomes. This information will be used to investigate the evolutionary significance of chromosome inversions. Genetic marker strains will be established from the village of Banambani in Mali. These strains will be selected so that they carry a rare (p less than or equal to 0.01) microsatellite allele. A population of 2,000 gravid females from one of these strains will be released back into the Banambani population. Dispersal, patterns of oviposition, establishment of progeny and patterns of mating among these progeny and the indigenous population will be evaluated by recapture. These efforts will provide direct estimates of gene flow (dispersal). The strategy for the development of competitive laboratory strains will be evaluated and, if established, their behavior in nature will be evaluated. Patterns of mating relative to chromosomal form will be evaluated by karyotyping any strain/wild hybrids. This effort will represent the first serious attempt to determine the fate of genes introduced into a natural population of a malaria vector.